For practice purposes we can divide repertoire string-crossing passages involving three strings into several different types:
REGULAR: broken chords, in which there is one note per string and the bow always goes to an adjacent string:
IRREGULAR: arpeggio type figures in which the bow always goes to an adjacent string but there is sometimes more than one note per string
GRASSHOPPER (WITH LEAPS): passages with jumps to non-adjacent strings:
A special discussion of leaps across multiple strings can be found here.
Compilations of exercises and repertoire excerpts involving three strings can be found for each of these types of passage:
REGULAR BROKEN CHORD PASSAGES: REPERTOIRE REGULAR BROKEN CHORD PASSAGES: EXERCISES
IRREGULAR ARPEGGIO PASSAGES: REPERTOIRE IRREGULAR ARPEGGIO PASSAGES: EXERCISES
3-STRING LEAP PASSAGES: REPERTOIRE 3-STRING LEAP PASSAGES: EXERCISES
Each passage/exercise can be practiced with many different bowings: slurred, separate, mixed, spiccato etc.
We can use the Three-String Chord Charts to create our own bowing exercises to reinforce the different 3-string crossing bowing (and left-hand) problems that we will find in the repertoire.
Very often repertoire passages passages will be a combination of 3 and 4-string crossings. These mixed passages are included in the Four-string Crossings section.